Many people carry and use personal mobile devices such as cellular phones, smart phones, portable audio players, tablets, laptop computers and so on. Many find that they inadvertently left behind their device at the location of a previous engagement. If several locations have been recently visited, it may be difficult to remember or even ascertain at which location the device was left. This can lead to great inconvenience, loss of property, loss of business opportunities, missed communications or any combination of these.